In a field of fine processing typified by semiconductor manufacturing, a photolithography process in which i-line with a wavelength of 365 nm is used as exposure light has hitherto been widely used.
As the resist material used in the photolithography process, for example, a resin composition containing a polymer having a carboxylic acid tert-butyl ester group or a phenolic tert-butyl carbonate group and a photoacid generator has been used. As the photoacid generator, ionic photoacid generators such as a triaryl sulfonium salt (Patent Document 1) and a phenacyl sulfonium salt having a naphthalene skeleton (Patent Document 2) and non-ionic acid generators such as an acid generator having an oximesulfonate structure (Patent Document 3) and an acid generator having a sulfonyldiazomethane structure (Patent Document 4) have been known. By allowing this resist material to be irradiated with ultraviolet rays, the photoacid generator is decomposed to generate a strong acid. Furthermore, by being subjected to post exposure baking (PEB), a tert-butyl ester group or a tert-butyl carbonate group is dissociated from the polymer by virtue of this strong acid, a carboxylic acid or a phenolic hydroxyl group is formed, and a part irradiated with ultraviolet rays becomes readily-soluble in an alkali developing solution. This phenomenon is utilized to perform pattern formation.
However, as the photolithography process becomes finer processing, since the influence of swelling becomes greater when the pattern of a light-unexposed part is swelled due to an alkali developing solution, it is necessary to suppress the resist material from being swelled.
For the purpose of solving these problems, there has been proposed a method of suppressing the swelling of the resist material by allowing an alicyclic skeleton, a fluorine-containing skeleton, or the like to be contained in a polymer in the resist material to make the polymer hydrophobic.
However, with regard to the ionic photoacid generator, since the compatibility against a hydrophobic material containing an alicyclic skeleton, a fluorine-containing skeleton, and the like is insufficient, there is a problem that sufficient resist performance is not exerted since the phase separation occurs in the resist material and the pattern formation results in failure. On the other hand, although the non-ionic photoacid generator is satisfactory in compatibility against a hydrophobic material, there are a problem that the sensitivity to i-line is insufficient and a problem that the allowance range is narrow since the heat-resistant stability is insufficient and the photoacid generator is decomposed by post exposure baking (PEP).